A composite charged particle beam apparatus includes a FIB column for irradiating a thin sample with a FIB and a GIB column for irradiating the thin sample with a GIB. The thin sample is placed on a sample stage, and a tilt unit tilts the thin sample about a tilt axis of the sample stage, the tilt axis being orthogonal to the FIB irradiation axis and being located inside a plane formed by the FIB irradiation axis and the GIB irradiation axis. A tilt sample holder is mounted on the sample stage and fixes the thin sample such that a cross-sectional surface of the thin sample is tilted at a constant angle with respect to the GIB irradiation axis and the azimuth angle of the GIB column can be changed by rotation of the sample stage.